1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for cleaning the inside of a chamber using a radio frequency (RF) plasma.
2. Description of the Related Art
In order to form a film on the surface of a wafer when manufacturing a semiconductor device, a chemical vapor deposition (CVD) method based on a gaseous reaction within a vacuum chamber is used. However, when using CVD, a film of unwanted, contaminating reaction products or by products is deposited all over the inside of the chamber, and more importantly, on the surface of the wafer itself. These contaminants affect the physical and chemical properties of the film deposited on the wafer, and generate particles which further contaminate the wafer. It is therefore necessary to remove the unwanted reaction product deposited inside the chamber after a certain number of wafers have been processed. A cleaning method using a plasma has been used to remove the unwanted reaction product from the inside of the chamber.
According to the contaminants plasma cleaning method, a plasma gas source is supplied to the chamber to be cleaned, and an electric field is applied, causing a cathode to emit electrons. The emitted electrons collide with the source gas, generating a plasma consisting of electrons, cations and variety of neutral species. This plasma strikes against and cleans the inner surface of the chamber.
The state of the art plasma cleaning methods use a constant pressure and a constant RF power. However, only certain parts of the chamber are cleaned, permitting contaminating reaction products to accumulate on other parts of the chamber over many deposition and cleaning cycles. Also, since adhesion between the accumulated deposited materials is weak, over time the deposited materials separate from or fall off of the surface of the chamber generating particles that reduce semiconductor device yield.
In order to prevent the accumulation of the contaminating reaction products, the typical cleaning cycle, in which the chamber is cleaned once every nine wafers, may be reduced. However, frequent cleaning reduces throughput and is inefficient.